The present invention relates to a vibratory feeder adaptated to receive and displace loose material, especially from narrow surfaces on to wide ones and conversely. A vibratory feeder provided with a transport chute in the form of a trapezoid having its working surface, i.e. the bottom of the chute, of a flat and smooth element is already known. This feeder is mainly used for the transport of fine-grained loose material.
Also known is a feeding arrangement with a trapezoidal chute delivering coarse-grained material from wide installations onto narrow ones e.g. slime from a screen on to a narrow conveyor, having the surface over which materials move and provided with a number of steps to prevent sticking of the material.
In order to maintain the required durability and increase the free vibration frequency of the chute, numerous plate or box-type ribs are provided under the bottom of the chute which together with the chute, form a flat lattice-type frame. Such a structure is also used in vibratory feeders that are provided with chutes of small dimensions. Due to the current developments in the field of mineral treatment installations, as revealed by a increase in capacity through the extension of their width, as for example, in heavy media separation plants, water jigs, screens, etc. where uniform feeding of these installations with raw material at 500-1500 tons per hour and more takes place. As a result a range of widths from 3 to 6 m has become necessary.
Acceptance of such materials from this type of installation and further transport on to narrow conveyors, into crushers, on to trucks and so on, give rise to the problems that also require solution. The need for creating conditions for a particularly smooth transport of material in order to avoid crushing of grains of coarse grained coal, for instance, during transport need also be considered.
It is a matter-of-course that under some conditions it may be advantageous to produce a feeder according to the invention with the bottom being it its plan view, trapezoidal in shape with rectangular segments attached to the narrower and wider base of the trapezoid. An abrasion-resisting profile lining is provided preferably with a corrugated surface and is placed on the bottom of the trapezoidal transport chute. The length and height of the wave depends on the grain size of the transported material. The lining is set at both sides of the plane of symmetry of the transport chute, so that the vertex of angle .beta. formed by the crests of the lining waves faces the narrower end of the trapezoidal chute. In order to prevent sticking of grains during transport of coarse grained material, deflecting plates that displace the grains towards the centre of the chute are fixed to the sides of the tapering trapezoidal chute. Those plates are asymmetrically distributed along the sides of the chute and form a free, zig-zag, tapering strip for grain flow.
The transport chute is mounted to an eight-bracket supporting frame placed under the bottom thereof, so that oscillating motion is transmitted from the drive to the chute. The frame consists of two oblong and two transverse roof-beams, the distance between the oblong roof-beams at the wider end of the chute being at least equal to half of the width of this end.
The feeder in an embodiment having a rectangular or widening transport chute, is provided with a built in grate at the convex portion of the chute near the discharge end. Also, the feeder rests on a structure of a building by means of elastic elements fastened to oblong and transverse roof beams of the frame of the building.
The most advantageous loading conditions for the feeder structure is created when the holders of the elastic elements are placed near the joint between the longitudinal and transverse beam.
The trapezoidal chute in the vibratory feeder, the longitudinal section of which is in the form of a horizontal letter "S", is employed to result in a number of technological and operational advantages, especially in installations having large chute widths.
As an essential feature of the invention, the structure should be substantially rigid and this is due to the use of a concave and convex surface form on the bottom of the transport chute.
The aforementioned involves certain reductions in plate thickness, from which the bottom is made, as well as, the reduction in the number of transverse stiffening elements on the chute area. The free vibration frequency of the bottom of the chute was also intensified, so in turn the dynamic load of the elements thereof, are decreased and the durability increased. Further operational advantages are also present. For example, the use of a concave surface near the feed end of the chute, for instance, raises the transport speed of material, which is profitable either when feeding material from a bunker with a small outlet area or in case of a not too large distance between the outlet and bottom of the chute.
The concave surface of the chute is also adapted to smoothly receive large grains of material, thanks to the braking action directed against the falling grains on a long path; this is essential for brittle and large mass materials, e.g. lumps of coal and metal ores.
The application of a surface fragment of the bottom of the chute with a small degree of inclination between the concave and convex part reduces the transport speed of material. This favors a uniform distribution of the transported material along the entire width of the trapezoidal chute, even in the absence of a profile lining.
Furthermore, technological advantages are also achieved due to the use of a convex surface directed downward at the discharge end. The inclination of the convex portion of the chute increases the speed motion of the transported material, thus reducing the weight of material on this part of the chute. This is advantageous either with tapering trapezoidal feeders or with widening ones, and particularly with feeders provided with a grate element at their terminal portion.
The application of a rigidly bracked frame with properly spaced longitudinal and transverse roof-beams, ensures regular transfer of forces from the drive to the chute. Despite a substantial increase in width of the chute, it is still possible to maintain loads on roof-beams as is the case with known feeder equipment. The fastening of elastic element holders at points of connection between the longitudinal and transverse roof-beams, reduces the magnitude of additional bending moments resulting from the reaction of static and dynamic forces of the supporting structure.